fix(ambient): handle string or u32 for Claude tool parameters (#133)

[quangdang46]

What

Every ambient cycle (end_ambient_cycle, schedule_ambient,
schedule_tool, and next_schedule.wake_in_minutes payloads) was
failing at the JSON deserialization layer with:

invalid type: string "0", expected u32

Claude tool calls occasionally serialize numeric arguments as strings
(e.g. {"compactions": "0"}) rather than JSON numbers. Our u32
fields rejected those calls before any logic ran, breaking ambient
mode entirely.

This addresses issue #133: #133

Changes

• src/tool/ambient.rs:
  • Imported Deserializer from serde.
  • Added two custom serde visitor helpers:
    • deserialize_string_or_u32 — accepts JSON number or numeric
      string, returns u32.
    • deserialize_string_or_option_u32 — same but returns
      Option<u32> and preserves missing/null.
  • Wired #[serde(deserialize_with = ...)] on:
    • EndCycleInput::memories_modified
    • EndCycleInput::compactions
    • NextScheduleInput::wake_in_minutes
    • ScheduleInput::wake_in_minutes
    • ScheduleToolInput::wake_in_minutes
• src/tool/ambient/tests.rs: 5 new regression tests:
  • test_end_cycle_input_accepts_stringified_u32_fields
  • test_end_cycle_input_still_accepts_native_u32_fields
  • test_schedule_input_accepts_stringified_wake_in_minutes
  • test_schedule_tool_input_accepts_stringified_wake_in_minutes
  • test_end_cycle_input_rejects_non_numeric_string (defensive: a
    non-numeric string must still fail loudly, not silently coerce
    to 0)

Tests

$ cargo test -p jcode --lib tool::ambient::tests::
test result: ok. 27 passed; 0 failed; 0 ignored

All pre-existing ambient deserialization tests still pass (numbers
flow through the new visit_u64 branch unchanged).

Acceptance criteria

• Claude tool calls with {"compactions": "0"} style payloads no
  longer fail at deserialization — src/tool/ambient.rs:122-204
• All four affected structs (EndCycleInput, NextScheduleInput,
  ScheduleInput, ScheduleToolInput) accept both forms
• Existing JSON-number form still works — covered by
  test_end_cycle_input_still_accepts_native_u32_fields
• Non-numeric strings still rejected — covered by
  test_end_cycle_input_rejects_non_numeric_string

Notes

• Ports the src/tool/ambient.rs portion of upstream PR
  Fix ambient serde bug: handle string or u32 for Claude tool parameters 1jehuang/jcode#173 by @zanni098.
• The docs/WINDOWS_SETUP.md hunk that upstream PR also bundles is
  unrelated content from upstream PR [Upstream #235] jcode fails to execute in Termux due to missing dynamic linker and LD_PRELOAD conflict #172 (= our issue [Upstream PR #172] Add Windows Setup and Troubleshooting Guide #132) and is
  intentionally NOT ported here. That doc will be ported separately
  if/when issue [Upstream PR #172] Add Windows Setup and Troubleshooting Guide #132 is picked up.
• Pre-existing clippy::question_mark warning in
  crates/jcode-tui-mermaid is unrelated and reproducible on
  master.